Electrode structures for thermionic devices



March 20, 1962 c. c. VODDEN 3,026,441

ELECTRODE STRUCTURES FOR THERMIONIC DEVICES Filed March 16, 1960 5 Sheets-Sheet 1 FI G.2. |Q| I08 7 9 7 BIO lO l|6 /N VE N 70/? cYR/L 5/1094 E5 DEN March 1952 c. c. VODDEN 3,02

ELECTRODE STRUCTURES FOR THERMIONIC DEVICES Filed March 16, 1960 3 Sheets-Sheet 2 FIG. 3. l7 9 9 I9 l8 6 CYP/L C/ FPLE/S if DEN H TTOFP/VEY March 20, 1962 c. c. VODDEN 3,026,441

ELECTRODE STRUCTURES FOR 'I'HERMIONIC DEVICES Filed March 16, 19 60 3 Sheets-$heet 3 //V VE/VTOF? C YP/L C HIQfiDDE N 9 T TOFPNF Y United States Patent ()fltice 3,025,441 Patented Mar. 20, 1962 3,926,441 ELECTRQDE STRUCTURES FOR 'IHERI /HONEC DEVICES Cyril Charles Vodden, Enfield, England, assignor to Associated Electrical Industries Limited, London, England, a British company Filed Mar. 16, 1960, Ser. No. 15,295 Claims priority, application Great Britain Mar. 25, 1959 3 Claims. (Cl. 313-261) This invention relates to electrode structures for thermionic valves, cathode ray tubes, and the like.

it is necessary in electrode structures for thermionic valves to maintain an accurate spacing between the electrodes and to ensure that the electrodes are rigidly held in spaced relation to one another.

A common way of achieving these objects in connection with electrode structure in which the cathode, anode and control electrode are concentric with one another is to provide on each electrode extensions of the support rods for the electrodes, which extensions are arranged to engage suitably spaced apertures in a mica spacer which is caused to engage the inner periphery of the wall of the envelope of the device. The nn'ca spacers are threaded on to the electrode structure after its assembly and as the assembly is introduced into the envelope the engage- :ment of the ends of the mica spacer with the inner wall of the envelope centres the inner wall of the envelope and holds it firmly therein.

In the case of a cathode ray tube electrode structure or gun it is necessary to maintain a co-axial relationship with the several electrodes of the gun. This has commonly been achieved by providing on the outer parts of the electrodes metal pins which are aligned axially on the electrode structure and are embedded into a glass rod which lies in a plane containing the axis of the electrode structure.

According to the invention, the electrodes in an electrode structure are held in predetermined spaced relationship by means of insulating members formed to locate between them rods pins extending from the electrodes, at least one of the insulating members being notched to receive and locate the rods or pins in spaced relationship and the insulating members being secured together to retain the rods or pins in the notches.

In the case of an electrode structure for a thermionic valve in which the electrodes are in co-axial relation with one another, rods which engage the insulating members are preferably formed by extensions of the support rods beyond the effective areas of the electrodes so that the insulating members thereby replace the mica spacers hitherto used on such structures as hereinbeiore referred In the case of an electron gun for a cathode ray tube, pins may be secured to the electrodes so as to extend outwardly therefrom, the pins being preferably arranged so that their axes lie in a common plane so that they can be held in the desired spaced relationship in notches formed in the face of one of the mutually co-operating insulating members.

The insulating members are conveniently in the form of rectangular bars of ceramic material, one of the bars having spaced notches formed in one face thereof, in which notches the rods or pins are located and are held therein by the application of the other bar to the notched bar. Ceramic material is conveniently used for the purpose owing to its ability to withstand heat without distortion and to be readily denuded of occluded gas. Furthermore, ceramic material may readily be machined to locate the pins or rods.

it the pins or rods are arranged with their longitudinal axes in a common plane, it is desirable for the notches to be provided in the face of one of the insulating members and for the other one to provide a flat surface so that when the insulating members are secured together all the pins are engaged by the flat surface of the insulating member which serves to clamp them in the notches. However, notches may, if desired, be provided in both the insulating members. if all notches are provided in one of the insulating members which is of ceramic material the other member may be of a material other than ceramic, provided that it is of a suitable and insulating nature.

The insulating members may be secured together by clips or hands spaced around the ends of the members and suitably located by means of grooves or notches formed in the periphery of the insulating members or by pins or rivets passing through the members.

in order that the nature of the invention may be understood more clearly, reference will now be directed to the accompanying drawings in which:

FIG. 1 shows the upper portion of an electrode structure for a thermionic valve provided with locating means for the electrodes in accordance with the invention,

FIG. 2 is a plan view of FIG. 1 to show the arrangement of the notching of the insulating members,

FIG. 3 is a plan view of an alternative form of the notched insulating member,

FIG. 4 is an end view showing one form of clip employed for securing the insulating members together,

FIGS. 5 and 6 show in plan and end view an alternative means for securing the insulating members together,

FIG. 7 is a perspective view of the upper end of an electrode system for a thermionic valve showing an alternative arrangement of insulating members for locating the electrodes in their desired positions and embodying the invention, and

FIG. 8 is a perspective view of a clip employed in the arrangement shown in FIG. 7 for securing the insulating members together.

Referring to PEG. 1, there is shown in perspective the upper end of an electrode structure of a thermionic valve, comprising a cathode l, a control grid 2, a screening grid 3, a space change grid 4 and an anode 5 of conventional construction. Located beyond the active portion of the electrodes are the insulating members 6 and 6' which serve to space and locate the electrodes from one another. The insulating member 6 is notched, as shown, on one of its faces toreceive rods extending from the electrodes. In the case of the grid electrodes 2 and 3, the rods 7 and 8, respectively, constitute extensions of the side support rods of these grids, whilst in the case of the cathode separate locating rods 9 are attached to the outer electron emitting portion of the cathode. Similarly to the ends of the grid anode 4, support rods lit, 16', respectively, extend beyond the active portion of those electrodes. The rods 7 it) are located in suitably spaced notches in the face of the insulating member 6 and are retained therein by the insulating member 6', the two members being held together so as to clamp the rods between them by means of clips 11 entered in grooves 11' formed adjacent the ends of the members 6, 6'.

One form of clip which may be employed is shown in FIG. 4 and consists of a pair of metal strips 12 having projecting flanges 13 which are secured together, e.g. by spot-welding.

An alternative method for securing the insulating members together is shown in FIGS. 5 and 6 and consists of a rivet pin 15 inserted through aligned bores in the members 6, 6 and secured in position by means of a thimble or eyelet 16 passed over the end of the rivet and secured thereto by spot-welding. Two or more such rivets may be used as may be found desirable.

In an alternative embodiment shown in FIG. 3, the

. are to engage. Thus, when two such insulating members are placed together the tongues 1'7 lying between the notches are in, or nearly in, contact with one another so that the rods located between them, of which two only are shown, are accurately located transversely of one another. It will be noted that the notches 18 are of slightly greater width than those at 19, the notches 19 being slightly wider than the diameter of the rod which is to be received in the notch. In this way tolerances on the separation of the support rods may be accommodated. it is desirable, but not essential, that the notches located at successive and greater distances from the centre line of the insulated member are in the form of standard and oversize notches, so that the tongues or lands 17 between them may be as large as possible.

Referring now to the construction shown in FIG. 7, the arrangement here shown employs a mica disc 24 which replaces the notched member 6 in the arrangement shown in 'FIG. 1. The rods extending from the electrodes are held against the face of the ceramic member 6 by means of the spaced notches 21 formed in the mica disc 20 which is located below the ceramic members 6, and extends in a plane normal to the face of ceramic member 6. The notches are formed along one edge of a rectangular apertur'e 22 punched in the mica disc so that the edges of the notches lie along a straight line. A very accurate spacing of the electrode rods can be provided in this manner. Mica disc 20 is held against the lower face of the ceramic member 6' by" means of clips 23, shown in FIG. 8. The clips are formed with lugs 24 which are spot-Welded, as indicated at 25 to pins 26 which pass through bores 27 in the ceramic member 6. The clips are provided with tongues 2% which pass through slots in the mica disc 29 and are folded under the disc to retain it in position on the clips. Preferably to hold the mica disc and the support rods firmly in position, a second ceramic member 29 is located below the mica disc, being held in contact therewith by a further clip 30 similar to clip 23. In order to prevent the tongues 28 from interfering with one another when two clips are employed, the tongues are located asymmetrically about the centre line of the clip, as indicated in FIG. 8. Mica disc 26 has projections 31 adapted to enable the disc to engage the inner periphery of a tubular envelope for the electrode structure and centre the structure within the envelope.

As mentioned above, in the case in which the invention is applied to the electron gun structure of a cathode ray tube, the support rods may be in the form of pins secured to the electrodes of the gun to prog'ect outwardly therefrom, the pins being located within the notches in one or both of the insulating members and held therein in the manner illustrated in connection with 1. In this case the insulating members will generally extend alongside the electron gun structure parallel to the longitudinai axis thereof.

What I claim is: I

1. In an electrode structure for thermionic valves and like devices, an insulating member having a flat face and at least two bores substantially parallel to said flat face and to the axis of the structure, spaced pins extending through said bores, electrode support rods located against said'face, a slotted mica spacing member extending in a plane normal to said face to hold the support rods thereagainst, spaced notches formed along one edge of one slot in said spacing member to engage and space corresponding electrode support rods along said face, and means for holding said mica spacing member adjacent the insulating member comprising a clip formed with lugs and tongues, said lugs being secured to said spaced pins and said tongues passing through another of said slots and being folded over to secure said spacing member to said clip.

2. In an electrode structure for thermionic valves and like devices, a pair of insulating members each having a flat face and at least two bores substantially parallel to said fiat face'and to the axis of the structure, spaced pins extending through said bores, electrode support rods located against said faces, a slotted mica spacing member located in a plane normal to the said face to hold the support rods thereagainst, spaced notches being formed along one edge of one slot in said spacing memher to engage and space corresponding electrode support rods along said faces, said mica spacing member being clamped against one of said insulating members by the pressure exerted on to the surface of said spacing member opposed to that adjacentto said one insulating member by the other insulating member which engages therewith, clips formed to provide lugs and tongues, said lugs being secured to said spaced pins, said tongues passing through the other of said slots and being folded over to secure said spacing member to said clips.

3. In an electrode structure as claimed in claim 2, Isjaid insulating members being in the form of ceramic ars.

References Cited in the file of this patent UNITED STATES PATENTS Woo Oct. 27, 1959 

